Conventionally, regarding a product formed by combining and integrating a coil spring and resin-molded article, the coil spring and resin-molded article manufactured separately are often assembled together and integrated in a later step.
As a general prior art, FIG. 9 shows a composite molded article in which a coil spring and resin-molded article manufactured separately are integrated in a later step. Referring to FIG. 9, reference numeral 1 denotes a coil spring; and 2, a resin bearing produced by injection molding.
The bearing member shown in FIG. 9 is mounted in a toner cartridge of an image forming apparatus (copying machine or printer) which is manufactured by the present applicant. FIG. 11 shows part of the toner cartridge which mounts the bearing member. In FIG. 11, reference numeral 30 denotes a bearing member; 31, a toner cartridge frame body; 32, a shaft member; and 33, a coil spring.
A pair of the bearing members 30 are mounted in the cartridge frame body 31 at an interval. The shaft member 32 is inserted from the openings of the bearing members 30 to hold the ends of the shaft member 32 by both the bearing members.
In this arrangement, the coil spring 1 and bearing 2 manufactured in separate manufacturing steps are integrated by press-fitting the coil spring 1 in the bearing 2 by using an assembling means such as an automatic machine.
When the coil spring 1 and bearing 2 are fitted by loose fitting, they are often integrated by using a means such as adhesion when necessary.
Japanese Utility Model Laid-Open No. 03-013853 discloses a technique for integrating a coil spring and resin-molded article, and Registered Japanese Utility Model No. 2525487 and Japanese Patent Laid-Open No. 5-147066 disclose a technique associated with insert molding.
However, with the conventional arrangement as described above in which the coil spring 1 is pressed into the bearing 2, when the coil spring 1 is being pressed into the bearing 2, the bearing 2 made of a resin material is chipped by the coil spring 1 to produce resin chips. When the resin chips separate from the bearing 2 and attach to another member, they sometimes cause a functional trouble of the toner cartridge. Also, the connecting strength of the coil spring 1 and bearing 2 may decrease, which is a serious defect such as an adverse influence on a bearing function.
Assume that the coil spring 1 and bearing 2 are to be assembled and fitted by loose fitting. In this case, when inserting the coil spring 1 in the bearing 2, the bearing 2 made of the resin material may not be chipped by the coil spring 1 to produce resin chips. However, to prevent the coil spring 1 from dropping from the bearing 2, the coil spring 1 must be fixed to the bearing 2 by using another means such as adhesion. This increases the number of steps and the cost.
When a product including a coil spring 1 press-fitted into a bearing 2 is to be assembled by an automatic machine or the like, coil springs 1 may be entangled with each other on the parts feeder and cannot be separated. Then, supply of the coil springs 1 becomes short, and the automatic machine stops frequently. The entangled coil springs 1 must be separated manually, which is cumbersome. In the steps of transporting and press-fitting the coil springs 1, since the coil springs 1 are flexible, the automatic machine or the like requires fine adjustment and is difficult to be stabilized.